Predicting motor improvement after stroke with clinical assessment and diffusion tensor imaging

Abstract

Reliable predictors of motor improvement in individual patients after stroke are scarce. Acute determination of upper limb Fugl-Meyer assessment (FMA) appears to have predictive value.1,2 This approach predicts that patients will improve approximately 70% of the difference between the maximum upper extremity FMA score and the score first tested for a given individual (recoverytypical). However, a significant subset of patients improves much less than predicted (recovery-atypical). Alternative models using other techniques like diffusion tensor imaging (DTI) 3,4 also fail to predict recovery in some patients. Here, we show that a combination of FMA and DTI obtained in the first weeks after stroke accurately discriminate between recovery-typical and recovery-atypical patients. In addition, we identify an alternative set of model parameters required for predictions in the recovery-atypical subgroup.We examined 25 patients (mean age 61 years, 11 female) with first ischemic stroke. Patients had a mean NIH Stroke Scale score of 11 (table e-1 on the Neurology ® Web site at Neurology.org). FMA 5 and DTI (appendix e-1) were obtained 2 weeks and 3 months after stroke onset. The FMA was performed by a trained occupational therapist blinded to the DTI results. Corticospinal tract (CST) asymmetry was calculated from the mean fractional anisotropy (FA) of the CST 3 :As with previous observations, 3,4 patients with greater CST asymmetry at 2 weeks had proportionally more severe motor deficits, both 2 weeks and 3 months after stroke onset (Spearman r , 20.8, p , 0.0001, figure 1, A and B). However, CST asymmetry was not significantly related to FMA improvement from 2 weeks to 3 months ( figure 1C). These findings were also confirmed when FA ispilesional /FA contralesional ratios were used as predictors rather than CST asymmetry.As expected, a majority of patients followed the FMA-based model predictions ( figure 1D; filled symbols), while a subgroup of patients exhibited recovery-atypical profiles ( figure 1D; unfilled circles). In order to further characterize the 2 patient subgroups, we computed the model residuals as the difference between the predicted FMA improvement and the observed FMA improvement. The residuals clearly differentiate recovery-typical ( figure 1E; filled bars) from recoveryatypical patients (unfilled bars). All recovery-atypical Ethan R. Buch, PhD Sviatlana Rizk, PhD Pierre Nicolo, MS Leonardo G. Cohen, MD Armin Schnider, MD Adrian G. Guggisberg, MD Figure 1 Fugl-Meyer assessment (FMA) and diffusion tensor imaging (DTI) predictors of motor improvementCorticospinal tract (CST) asymmetry at 2 weeks correlated with the severity of motor deficits at (A) 2 weeks and (B) 3 months after stroke, but not with (C) the change between these 2 time points. (D) The model DFMA 5 0.7*(66-FMA intial ), represented by a continuous line, predicted future FMA improvement in most patients (filled symbols), but there was a significant recovery-atypical subset (n 5 9; unfilled circles). (E) Recovery-atypical patients were def...

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